i would like to think i know a good amount of stuff about cars and how they work but the whole gearing means. like 4.11 that kind of stuff. i have been looking for a chart or some thing that would tell me what gear ratio is good for things. as if i wanted to run a high torque engine for a street car or if i was building a car for pro mod and a drag way. or even if theirs a formula for breaking down the ratio's so i can understand them. if any one can help me that would be great.

 

if you google that stuff you will find all kinds of calculators, and equations.

 

The very basics... driveshaft rotates 4.11 times for every ONE rotation of the tire (for 4.11 gears of course)...higher the number, the LOWER the gearing. Not sure if this is what you were asking.

 

Basically, the higher the number, the higher engine revs will be at the same speed. Like my car has 4.11 rear end, so at 60 MPH I am right around 3000 RPM. This is good for the quarter-mile but bad for highway cruising (high revs mean less gas mileage).

You have three things that are "multiplying" on top of each other. The engine revolutions get multiplied by what gear you're in to spin the driveshaft, then the driveshaft's RPMs get multiplied by the rear end. So, if the engine is at 1000 RPM, and first gear is 3.00 (or three-to-one) the drive shaft is then turning at one-third the Engine, or 333 RPM. Then goes through the rear end which is (say) 3.00 then the wheels are turning at another one-third the driveshaft, 111 RPM. If that rear end had been 4.11 then the driveshaft's 333 RPM would turn the wheels at roughly 81 RPM.

If the transmission gear you're talking about is less than 1.00, then it's called overdrive and the driveshaft is turning less than once per engine RPM. So let's say the engine is at 1000 RPM, and 5th gear is overdrive and it's a 0.75, (or three-quarters to one) the driveshaft is at 1333 RPM. Run that through your 4.11 rear and the wheels are at 324 RPM. But, the 3.00 rear end would be turning the wheels at 444 RPM - this car is going faster but the engine is going slower and using less gas... but also if you stomp on it (without shifting) will not accelerate as strongly.

 

Divide the number of teeth on the pinion gear into the number of teeth on the ring gear and you will get the gear ratio. Higher number equals more engine rpm lower number equals lower rpm.

 

The larger the gear ratio (ie, 4.11 compared to a 3.36) the greater the torque multiplication at a specific engine RPM...but it causes the engine to rev higher to get the same vehicle speed. So, a 4.11 diffy will give you better take-off torque, but the engine RPM at 60 mph will be proportionally higher than a car with the 3.36. Does that help?

 

the higher the number, the higher the engine RPM at the same MPH
.. the result is a bigger kick due to the torque multiplication vs a smaller numbered ratio car..

I personally want to keep my rpms down and use my car as only a cruiser. plus I don't want wear and tear on the engine... a very expensive engine that my car would take a big hit in value if I blow it up... so I run a 2.73. it just depends on what you have and what you want to do..

 

thanks all the info you people have gave has helped alot! im not looking for a cruising gear set up. i want to build a c3 to run at a near by dragway. but still run it in the pro street class. and it would have to pass inspection witch is a pain here in maine they are very picky on what u put on the road. i want to run a bbc from world casting. its a 540 cubic inch engine with a duel quad 850 demon cfm carbs. torque is what im shooting for and from what you have told me i can now use that info to put the power to the road. thanks

 

Big blocks are torque monsters and if you run too low of a gear ratio you will only eat up the tires while not moving very far. For instance, my Corvette came with the LS-5 454 producing 455 foot pounds of torque and a 3.08:1 gear ratio.

What this does is allows the car to be streetable in both city and highway driving. The incredible amount of torque makes 4th gear very usable on city streets while keeping rpms low on the highway.

What you will need for the strip is a gear that will get you out of the hole quickly without going up in smoke when you floor it.

You may find that changing to a transmission like the T56 will help more than anything. The T56 has really low first through fourth gears and 2 overdrive gears for streetability. The best of both worlds.

If you prefer an automatic for racing, the 4L60E or any of the newer overdrives would do as well.

cc

 

i would like to stick with the 4 gear stick. that and do any of you know any thing about the tigershark rear end for the c3 vetts when it comes to useing it for on the drag? but i still want to use it on the road and a four link will most likely not get a sticker (i want to run in the streat heat)